1. Field of the Invention
The present invention relates to a contact and an IC socket using the contact, and more particularly to a contact having two objects to contact, placed above and below thereof, and to an IC socket using such the contact.
2. Description of the Related Art
It is a conventional practice to use a contact having two objects-to-contact above and below thereof (e.g. an IC package placed above and a printed-wiring board placed below) as disclosed in Japanese Patent Laid-Open No.H10-125428 and Japanese Utility Model Registration No. 3,078,529, as contact for an IC socket to mount and test an integrated circuit package (referred to as an “IC package”, from now on) compatible with high frequency. Those contacts are each structured to be placed in elastic contact with both of an IC package mounted on the IC socket and a printed-wiring board such as a test board so that electrical connection is obtained with both the IC package and the printed-wiring board. Meanwhile, those contacts are devised to shorten the signal path length of a current (signal) flowing through the contact and reduce the inductance thereof, in order to cope with high-frequency signals.
The contact, having such two objects-to-contact, requires an increased spring constant in order to stably keep the electrical contact with the IC package and the printed-wiring board. In order to increase the contact spring constant (i.e. increasing the contact springiness), the contact must be increased in length at the elastically deforming portion thereof. This however increases the size of the contact and hence the signal path length along which the signal passes through the contact. Due to this, there encounters the increasing inductance over the signal path formed through the contact, resulting in a fear that the signal is not to be exchanged correctly between the printed-wiring board and the IC package due to the occurrence of noises, etc. Thus, the contact is difficult to design because of the contradictory in increasing the contact springiness and making the contact compatible with higher frequency.
Moreover, the IC package recently has an increased number of external contacts. As the pitch of external contact decreases, the contact itself is required smaller in size. There is a difficulty in obtaining a contact having a high springiness to keep the contact pressure between the contact and the object-to-contact at predetermined pressure.
Meanwhile, because of having two objects-to-contact, the contact is required to provide stable electrical connection for both of the objects. This requires the accuracy in arranging the contact and hence the significant time in the manufacture.
Both the existing contacts are not easy to reduce the size in obtaining higher springiness. Meanwhile, the contact disclosed in Japanese Patent Laid-Open No.H10-125428 is not easy to fit in a spring-receiving chamber of the socket body. The contact disclosed in Japanese Utility Model Registration No. 3,078,529 requires fitting accuracy and arranging solder bumps. In each of the arts, time is needed significant in the manufacture.
In view of the foregoing problems, it is an object of the present invention to provide a contact having two objects-to-contact above and below thereof which is easy to reduce the size and capable of obtaining high springiness and contacting electrically with both two objects-to-contact with stability and is easy to fit in an IC socket, as well as an IC socket using the contact.